Field of the Invention
This invention relates to biosensor for point-of-care (POC) diagnostics, and in particular, it relates to a biosensor using a decoupled microfluidic device that employs particle aggregation and size-separation.
Description of Related Art
High-sensitive, rapid and inexpensive biosensors, i.e. sensors for detecting biomolecules, such as DNA or protein sensors, are desired for point-of-care (POC) diagnostics. In conventional biosensors, the capture step and the detection step are coupled to each other. In the capture step, the biomolecules to be detected are captured by capture agents in a chamber of the biosensor; in the detection step, the captured biomolecules are detected. In the case of such capture and detection coupled biosensor, there is often a tradeoff between one (e.g. capture) and the other (e.g. detection) and both cannot be optimized simultaneously.
A team at Stanford Genome Technology Center developed an ultra-sensitive electronic microfluidic technique, referred to as “decoupled” digital detection. Using this technique, the team has demonstrated an attomolar level limit of detection (LOD) with palm-top size devices. See Mok et al., Digital microfluidic assay for protein detection, Proc Natl Acad Sci USA 2014 Feb. 11; 111(6):2110-5 (“Mok et al., PNAS 2014”); see also US 2011/0312518 A1. In this decoupled system, the capture chamber and the detection chamber are completely separated physically, which offers a large degree of flexibility in tailoring each chamber. Noises due to non-specific binding can be reduced, resulting in increased sensitivity. However, this technology is slow, requiring a relatively long time for the capture reaction (on the order of one hour) due to the low concentration of capture antibodies and the small volume of the capture chamber.